Effect of silicone vapour and humidity on contact reliability of micro relay contacts

Contact resistance characteristics of a micro relay with Au(90wt.%)-Ag(10wt.%) cladded contacts were examined in air containing silicone vapour and in air mixed with silicone vapour and high humidity. Electrical conditions for resistive loads of the contacts were covered with four regions such as bridge region, first micro-arc region, second micro-arc region and arc region. Concentrations of the silicone vapour were selected both 1300 ppm which gives saturation of the vapour, and 7 ppm which is the safety level for the contact reliability. Moreover, effect of humidity on dynamic contact resistance characteristics in the silicone environment was also studied. As results, a boundary of occurrence of the contact failure in the relationship between voltage and current was found. This boundary was given by a certain electrical power. Number of operations to failure was found to be inversely proportional to electric power. Under the condition of high humidity, low contact resistance maintained longer operation time than low humidity.